关键词: 光周期, 布氏田鼠, 长爪沙鼠, 体重, 能量代谢, 基础代谢率

Abstract: Body weight , basal metabolic rate (BMR) , and energy metabolism were measured under long photoperiod (16L∶8D , LD) and short photoperiod (8L∶16D , SD) for acclimating Brandt's voles (Microtus brandti) and Mongolian gerbils (Meriones unguiculatus) . Animals were transferred from LD to SD conditions for 6 weeks for voles and 7 weeks for gerbils. Body weights were measured at 32 day intervals at first two weeks and at last 3 days of each week thereafter. Energy intake , digested energy , and metabolizable energy were determined by food trials (metabolic cage) with 32 day intervals. BMRs were measured by using closed circuit respirometer within thermoneutrality at the beginning and the end of acclimation. Under LD and SD conditions, both voles and gerbils tended to increase their body weights , increasing faster within the first 2 weeks and then slowing down , and became stable after 3 weeks. However , the magnitude of changes is different between LD and SD conditions, and also between voles and gerbils. Under SD conditions , body weights were increased by 37 % for voles and 11 % for gerbils , and those were lower than under LD conditions (47 % for voles and 25 %for gerbils). This suggests that there is a sensitive time to photoperiod and SD could constrain the increase in body weight for both species. There were no effect of photoperiod on energy intake, digested energy , and metabolizable energy for both voles and gerbils. Photoperiod also had no significant effect on BMRs for both species. These results suggest that short photoperiod can cue both Brandt's voles and Mongolian gerbils to decrease their body weights and thus decrease the absolute energy requirement per animal for winter survival in their natural environments.

Key words: Photoperiod, Brandt's vole (Microtus brandti), Mongolian gerbil ( Meriones unguiculatus), Body weight, Energy metabolism, Basal metabolic rate